JP2005256237A - Printing coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide ultrathin or <60 g/m2 offset-printing coated paper which maintains conventional offset printing suitability, does not cause a print through phenomenon of a water-based ink, even when subjected to a multicolor printing treatment and then to an on-demand method high speed ink jet printing system, and exhibits a high printing concentration. <P>SOLUTION: This printing coated paper having a basis weight of 40 to 55 g/m<SP>2</SP>and produced by coating both the sides of base paper with a coating liquid containing a pigment and a binder as main components to form the coating layers is characterized by forming the coating layers in a quantity of 5.5 to 10 g/m<SP>2</SP>per one side on both the sides of base paper which has a contact angle of 55 to 70 degree to a liquid having a surface tension of 45 mN/m for a contact time of 0.1 sec and a maximum fine pore diameter of 1 to 10μm determined from a bubble point value measured according to JIS K 3832 "a method for testing the bubble points of microfiltration membrane element and module". <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a coated paper for printing of less than 60 g / m ² , and more particularly to a coated paper for offset printing applied to a high-speed inkjet printing system after full-color offset printing.

  In recent years, an ink jet printing method has become widespread in commercial printing as a recording method. In the ink jet recording method, since ink droplets fly at high speed from a printer nozzle toward a recording medium such as paper and adhere to the recording surface, images and characters are recorded. Have been developed suitable for various recording methods. Furthermore, a high-speed inkjet printing system based on an on-demand system has been developed, and further growth is expected in the future due to improvements in quality and efficiency.

Even in the conventional offset printing paper field, the printing industry accompanying the demand for resource saving due to the recent increase in national environmental protection awareness, an increase in direct mail and catalog sales, etc. With regard to offset printing paper for applications where there is a strong demand for resource saving and cost reduction in the publishing industry, weight reduction is rapidly progressing, and offset printing paper of less than 60 g / m ² is drawing attention.

In general, as printing paper having a basis weight of about 25 to 60 g / m ² , surface-sized plain paper (non-coated paper) or coated paper (about 12 g / m ² pigment coated on both surfaces) Finely coated paper and high-quality base ultra-light coated paper were used.

In addition, with regard to printed materials, there is a tendency for visual and high-grade printing to be increasingly demanded, and even for printing paper of less than 60 g / m ² , offset printing suitability similar to general printing paper is required. In order to meet the requirements of its own smoothness and printing gloss, printing paper provided with a coating layer composed of a pigment and a binder is often used.

  Recently, however, many applications combining the above-described ink jet printing have been seen. For example, after offset printing of fixed information in full color, variable data such as address and customer personal information is printed using an on-demand high-speed inkjet printing system. However, paper for inkjet printing cannot be used as it is for conventional full-color offset printing.

  This is because, when offset printing is performed on a conventional printing paper for an ink jet recording system, it takes time to set the ink. B) The smoothness is poor and the gloss of the image area is insufficient. C) Since it is porous, the scratch resistance is inferior, and the surface layer is taken on the plate during offset printing. D) A pigment having a high oil absorption property is applied, and only the vehicle in the ink for offset printing is absorbed rapidly, so that the pigment in the ink is difficult to transfer. E) A cationizing agent is added, which imparts hydrophilicity to the hydrophobic portion of the offset printing plate and causes emulsification of the ink. In the past, printing papers suitable for each method have been used properly, but printing papers suitable for both methods are strongly desired.

Printing paper suitable for both types includes printing paper with a binder resin and fine particle silica as the main component on a base paper, and pigments and binders mainly composed of silica. A printing paper to be coated is disclosed.
JP 2001-301316 A JP 2002-127487 A

The ink transfer amount when the absorption time is 0.7 seconds by the Bristow method is 9.0 ml / m ² or more, and the coating for printing contains 30% by mass or more of light calcium carbonate as a pigment for forming the coating layer. Paper is disclosed.
JP 2002-138391 A

However, the printing paper suitable for both of these types is limited to thick coated paper having a basis weight of 100 g / m ² or more, and there is no printing paper having a basis weight of less than 60 g / m ² as described above. It was the current situation.

The coated paper for offset printing is designed in consideration of printing with an oil-based offset printing ink, and therefore resistance to penetration of water-based ink in ink jet printing is not considered at all. Therefore, when ink jet printing is performed on a normal coated paper for offset printing, the water-based ink easily penetrates into the paper. In particular, coated paper for printing with a weight of less than 60 g / m ² such as ultra-light coated paper is thinner, so water-based ink that has penetrated into the paper easily reaches the back surface, causing ink back-off. It becomes easy to do.

Using five general-purpose inkjet printers (manufactured by Epson, product name Karario PM-770C), the applicability of inkjet printing in the OHP sheet printing mode was actually evaluated for five types of commercially available ultralight coated paper and two types of finely coated paper. As a result, as shown in Table 1, both the ultra-light coated paper and the fine coated paper had poor printability. Table 1 also shows the physical properties of the paper, such as the resistance to air permeability, the degree of squeecht size, and the surface contact angle with a liquid having a surface tension of 45 mN / m. Although there was a slight difference in the dot shape, no relationship was found between the difference in dot shape and the physical properties of the paper. Since the ink backside was different from the on-demand printing system equipped with a drying device, it was necessary to make a relative evaluation between the samples. there were. In relation to the physical properties of the paper such as the air resistance, the squeecht degree, and the surface contact angle, it was found that the higher the air squeeze resistance than the skeight sizing degree, the more the back-slip was reduced. Thus, the ultra-light coated paper, which is a coated paper for printing of less than 60 g / m ² , and the fine coated paper do not take into account the back leakage prevention measures of the water-based ink, including the printability of the water-based ink, There was nothing applicable to a high-speed inkjet printing system after offset printing.

In addition, it is desired that the coated paper for printing of less than 60 g / m ² is inexpensive in terms of manufacturing cost, and the coated paper for printing of less than 60 g / m ^{2 that} can support on-demand (inkjet) printing. However, it is preferably produced by a conventional production method without using a significant change in formulation or special processing means.

Therefore, the object of the present invention is to maintain the suitability of conventional offset printing without greatly changing the current manufacturing method, and even when applied to an on-demand inkjet printing system after multicolor printing, An object of the present invention is to provide a coated paper for offset printing of less than 60 g / m ² that exhibits no printing and exhibits a high printing density.

  When proceeding with the examination of the above problems, the present inventors differed from the air permeability resistance and sizing degree of the coated paper depending on the size of the through-hole of the base paper before coating and the amount of sizing agent added. We paid attention to the surface contact angle of the coming base paper.

  As a result of intensive studies, the present inventors have found that when the beating degree of the pulp fiber for papermaking is within a specific range, the maximum pore diameter, which is an index of the size of the through-hole of the base paper, is below a certain level, When the coating layer provided on the base paper whose surface contact angle is within a specific range is within a specific coating amount range, the back-off of water-based ink in a high-speed inkjet printing system is eliminated and high printability is exhibited. The present invention has been found.

The invention of claim 1 is a coated paper for printing having a basis weight of 40 to 55 g / m ² in which a coating layer is provided by coating a coating liquid mainly composed of a pigment and a binder on both sides of a base paper. Contact time with a liquid having a maximum pore diameter of 1 to 10 μm and a surface tension of 45 mN / m obtained from a bubble point value measured according to JIS K 3832 “Bubble Point Test Method for Microfiltration Membrane Element and Module” 0.1 second A coated paper for offset printing, wherein a coating layer is formed at 5.5 to 10 g / m ² per side on a base paper having a contact angle of 55 to 70 degrees.

The maximum pore diameter is an equation using a bubble point value P ((kPa): pressure when the first bubble is generated) measured according to JIS K3932 “Bubble Point Test Method for Microfiltration Membrane Elements and Modules” ( This refers to the pore diameter d determined from 1), and examples of the measuring instrument include Palm Porometer CSF-1100A manufactured by Porous Materials.
d = (4cosφBγ) / P (1)
φ: Contact angle, B: Capillary constant, γ: Liquid surface tension That is, the maximum pore diameter is a measure of the diameter of a bubble through which a sheet can pass, and a method of measuring the maximum through-hole of the sheet Suitable as

  In the invention of claim 2, the base paper is made by internally adding an alkyl ketene dimer sizing agent as a filler and a sizing agent to a pulp fiber for papermaking having a shopper freeness of 55 ° SR or more, and the coating layer is a coating liquid. The coated paper for offset printing according to claim 1, which is provided by on-machine coating.

  In the invention of claim 3, the coating layer is 10 to 30 parts by mass of the binder per 100 parts by mass of the pigment, the hydrophobic resin component of the binder is 10 parts by mass or more per 100 parts by mass of the pigment, and the hydrophobic resin component of the binder and the hydrophilicity 3. The offset printing coated paper according to claim 1, wherein a mixing ratio of the resin components is 45:55 to 72:28. 4.

The coated paper for offset printing of the present invention is shifted to a slightly thicker coating layer range than the conventional ultra-light coated paper, so that the offset printing suitability is improved, and after the fixed information is offset printed in full color, Even when variable data such as personal information is printed by an on-demand high-speed ink jet printing system or the like, the water-based ink does not dull even though the basis weight is low, and a good printing result can be obtained. Accordingly, the present invention provides a coated paper for offset printing of less than 60 g / m ² having ink jet printing suitability in an on-demand printing system and capable of full color printing.

Furthermore, according to the present invention, the coated paper for offset printing of less than 60 g / m ² can be produced without greatly changing the conventional production method, so that it can be produced efficiently.

The basis weight of the coated paper for offset printing of the present invention is 40% from the viewpoint of satisfying demands for resource saving, reduction of mailing charges in applications such as direct mail, etc., and securing a sufficient amount of information. It is limited to ˜55 g / m ² . Preferably, the basis weight is 45 to 55 g / m ² . If the basis weight is lower than 40 g / m ^2, it is difficult to prevent the back side of the water-based ink from being lost even by the present invention.

Coated paper for offset printing of the present invention, per side 5.5~10.0g / ^{m 2,} but preferably is formed on the surface of the base paper a coating layer of 6.0~9.0g / ^{m 2,} It is desirable that the base paper before coating has the following configuration.

  The pulp used for the base paper of the coated paper for offset printing of the present invention should be used by mixing chemical pulp such as NBKP and LBKP, non-wood pulp such as hemp, kenaf and bamboo, and also waste paper pulp. Can do. Preferably, NBKP and LBKP are used alone or in combination.

  The pulp beating degree is particularly important because it is related to the size of the through hole of the base paper and the air resistance. When pulp having a freeness of 55 ° SR or more is used, it is possible to produce a base paper having an appropriate air resistance without a large through hole (pinhole) in which the maximum pore diameter described later exceeds 10 μm. , Giving suitable air resistance after coating. The upper limit of the freeness is not particularly limited, but 75 ° SR or less is preferable in consideration of the paper-making property of the base paper. Therefore, the range of the beating degree of the pulp used for the base paper of the present invention is preferably a shopper freeness of 55 to 75 ° SR, more preferably 60 to 75 ° SR.

  Full color offset printing paper is usually required to have a high opacity of 80% or more, and the base paper in the present invention preferably has an opacity of 70 to 80%. Therefore, the base paper is internally mixed with a filler mixed with pulp, and the internally added filler has an effect of preventing the occurrence of back leakage because the gap between the pulp fibers is filled and the through holes are made small. The filler is not limited by the type and shape, and calcium carbonate, kaolin, titanium dioxide and the like can be used alone or in combination. In the present invention, it is preferable to use a mixture of calcium carbonate and titanium dioxide, and the amount of internal addition is preferably 10 to 30% by mass, more preferably 15 to 25% by mass with respect to the mass of the base paper. If it is less than 10% by mass, not only the opacity required for offset printing paper and inkjet printing paper cannot be fully satisfied, but also the effect of filling the gaps between the fibers and reducing the through holes cannot be expected. If it exceeds 30% by mass, the stiffness and strength of the paper become weak, which is not preferable.

The surface contact angle at a contact time of 0.1 second with a liquid having a surface tension of 45 mN / m of the base paper is preferably 50 to 70 degrees, and more preferably 55 to 70 degrees. If the surface contact angle is 50 degrees or more, when inkjet printing is performed on the coated paper for offset printing, it is possible to prevent the aqueous ink that has penetrated the coating layer from penetrating into the inside of the base paper near the surface of the base paper. Therefore, it is preferable to prevent the occurrence of back leakage. However, if the surface contact angle is less than 50 degrees, it is difficult to prevent the water-based ink from penetrating into the inside of the base paper. A surface contact angle exceeding 70 degrees is not necessary, which increases the cost and is not preferable. As for the sizing agent internally or externally added to the base paper, as long as a surface contact angle of 50 to 70 degrees at a contact time of 0.1 second with a liquid having a surface tension of 45 mN / m can be obtained, an alkyl ketene dimer system, styrene acrylic It can be used without any particular limitation, such as a system or a styrene system. It is also possible to use both internal and external additives. The process of adding a sizing agent and applying the coating layer on-machine is most preferable from the viewpoint of manufacturing cost. In that case, from the viewpoint of the adhesive strength of the coating layer, the slow-acting property has a slow onset of size. In general, alkyl ketene dimer sizing agents are used. When the basis weight of the base paper is 30 g / m ² , the amount of internal addition is adjusted with 3.5 seconds or more as a standard for the degree of sizing. When the basis weight is 45 to 50 g / m ² , the steticht size of the offset printing coated paper obtained by coating is 5 to 10 seconds.

  Other base papers may be combined with paper strength enhancers, wet paper strength enhancers, fixing agents, colorants, whitening agents, yield improvers, antifoaming agents, pH adjusters, etc. Can be used.

  For the production of the base paper, a general long net paper machine is preferably used, and a twin wire type or on-top type long net paper machine is particularly preferred in which the difference between the front and back sides is reduced.

  When the size of the through hole of the base paper obtained in the paper making process is expressed as the maximum pore diameter, the maximum pore diameter of the base paper in the present invention is preferably 10 μm or less, and more preferably 8.5 μm or less. The maximum pore diameter decreases as the base paper basis weight increases and the pulp beating process proceeds, and it becomes easier to prevent the back side of water-based ink from being removed. The lower limit of the maximum pore diameter is not particularly limited, but the range of the maximum pore diameter of the base paper in the offset printing coated paper of the present invention is preferably 1 to 10 μm, more preferably 1 to 8.5 μm. It is.

  The standard of the air resistance when the maximum pore diameter is 10 μm or less is preferably 55 s or more, and more preferably 60 s or more. The upper limit is not particularly limited, but is preferably 250 s or less in consideration of papermaking properties. Incidentally, the maximum pore diameter of a base paper made by adding a filler to a pulp beaten to a shopper freeness of 30 to 40 ° SR (430 to 310 CSF) in the same manner is 20 to 30 μm. When the beating process was advanced and pulp having a shopper freeness of 72 ° SR (about 65 CSF) was used, the air resistance was 220 s and the maximum pore diameter was 1.08 μm.

  From the above, since the base paper in which filler and sizing agent are internally added to highly beaten pulp fibers has a small maximum pore diameter and high resistance to penetration of aqueous ink due to the developed size, The coated paper for offset printing obtained by applying to the base paper can prevent the back-off of the water-based ink in the on-demand type high-speed inkjet printing system.

  As an example of the blending of the base paper, NBKP 40% by mass and LBKP 60% by mass are beaten to 65 ° SR with a shopper freeness, then 13% by mass of precipitated calcium carbonate and 2% by mass of titanium dioxide as a filler, and alkyl as a sizing agent Examples thereof include a paper stock in which a ketene dimer sizing agent is added to 1% by mass of pulp and a small amount of cationic starch is internally added. Using this stock, the base paper for offset coated paper of the present invention can be obtained by making a paper with a predetermined basis weight using an on-top type long paper machine.

  A coating liquid mainly composed of a pigment and a binder is applied to both surfaces of the obtained base paper to produce a coated paper for offset printing of the present invention. As for the composition of the coating solution, a coating solution having a standard configuration used in the production of ordinary ultralight coated paper or fine coated paper can be used. The coating method is not particularly limited, and can be applied using a normal gate roll coater or blade coater.

The coating amount is preferably 5.5 to 10 g / m ² , more preferably 6.0 to 9.0 g / m ² per side. If it is less than 5.5 g / m ² on one side, the coating layer that covers the surface of the base paper may have a large variation in thickness or may not be completely covered. This is not preferable because the variation in the printing density is large and density unevenness of printing due to feathering or bleeding tends to occur. Even in offset printing, ink acceptability varies, which may cause a decrease in print quality, which is not preferable.

On the other hand, if it exceeds 10 g / m ² on one side, it is not preferable because the basis weight of the base paper has to be reduced, although the printing quality can be further improved in offset printing. Also, the amount of ink that stops on the surface of the coating layer due to the sinking of the water-based ink in ink jet printing is reduced, which may cause a decrease in print density, which is not preferable.

  As described above, a wide range of general configurations can be used for the coating liquid composition. As the pigment used in the coating liquid, those having an oil absorption of 20 to 50 ml / 100 g which are used for ordinary offset printing paper are mainly used. Pigments exceeding 50 ml / 100 g of oil absorption, especially around 100 ml / 100 g, such as certain calcium carbonates, silicas, and aluminas that have a high oil absorption, such as those used in the coating layer of coating type inkjet paper If the pigment content exceeds 30% of the total, it is difficult to obtain print quality suitable for gloss type offset printing. The types of pigments that can be used include various grades of kaolin for coating, light and heavy calcium carbonate, aluminum hydroxide, titanium dioxide and the like. A combination of kaolin and calcium carbonate is most commonly used as a pigment having high offset printing suitability, and is particularly preferable in view of production efficiency. For the purpose of improving ink setting property and printing gloss in offset printing, it is usual to use a pigment having an oil absorption of 50 ml / 100 g or more, for example, delaminated kaolin, plastic pigment, etc. within 15% of the whole pigment. It is generally performed in the production of coated paper for printing and is one of the preferred configurations for the present invention.

  As binders used for the coating layer, various latexes such as styrene-butadiene, styrene-acrylic, acrylic, vinyl acetate-acrylic, ethylene-vinyl acetate, synthetic binders such as polyvinyl alcohol, esterified starch, One or more of various starches such as oxidized starch, natural binders such as casein and gelatin, and cellulose derivatives such as CMC can be appropriately selected and used. These binders are used in the range of 10 to 30 parts by mass, more preferably 15 to 25 parts by mass per 100 parts by mass of the pigment. In this invention, it is preferable to mix | blend 10 mass parts or more of hydrophobic resin components with respect to 100 mass parts of pigments. If the blending amount of the hydrophobic resin component is less than 10 parts by mass, it is not preferable because a piling due to insufficient surface strength is likely to occur in offset printing. However, if the ratio of the hydrophobic resin component in the binder exceeds 72% by mass, the absorption of the water-based ink is delayed and printing stains are likely to occur, and it is preferable to avoid this if possible. Accordingly, it is more preferable to use a hydrophobic resin component such as styrene-butadiene latex and a hydrophilic resin component such as phosphate esterified starch in a ratio of 45:55 to 72:28.

  Furthermore, this coating layer has a viscosity modifier, a water retention agent, a lubricant, a pH regulator, a surfactant, a printability improver, a water resistance agent, a sizing agent, a fluorescent whitening agent, a colorant, a dispersant, an antifoaming agent. Various auxiliary agents such as an agent and a fragrance can be added as necessary.

In this invention, the coating liquid which has a pigment and a binder as a main component is apply | coated to both surfaces of a base paper, and a 5.5-10 g / m < ² > coating layer is formed per single side | surface. The application of the coating liquid is preferably on-machine coating from the viewpoint of production cost, but off-machine coating is also possible.

  When on-machine coating is applied directly to the base paper, if the coating layer is provided on the surface of the base paper before the size of the base paper is fully developed, the coating liquid, especially the binder component, partially penetrates the base paper. Therefore, the hydrophobic resin component is preferable because it inhibits the penetration of the water-based ink and is effective in preventing back-spotting.

  The coated paper obtained is subjected to a surface smoothing process according to the intended offset printing application with a gloss type or mat type using a generally known calendar processing apparatus such as a super calendar, a soft nip calender, or a gloss calendar. . The smoothness after calendar processing is 50 to 200 seconds for the mat type, and 500 to 2000 seconds for the gloss type.

The coated paper for offset printing of the present invention has a surface contact angle of 50 to 65 degrees at a contact time of 0.1 seconds with a liquid having a basis weight of 40 to 55 g / m ² and a surface tension of 45 mN / m, and air permeability resistance. It has a characteristic of 1,800 to 15,000 s.

The coated paper for offset printing of the present invention has high offset printing aptitude, and even when variable information is printed by an on-demand type high-speed inkjet printing system after the fixed information is offset printed in full color, Regardless of the amount, the water-based ink does not dull and a good printing result is obtained. Accordingly, the present invention provides a coated paper for offset printing having an inkjet printing suitability in an on-demand printing system and having a color density of less than 60 g / m ² for multicolor printing. Furthermore, according to the present invention, the coated paper for offset printing of less than 60 g / m ² can be produced efficiently.

<Experimental Examples 1-9>
A pulp fiber slurry having a shopper freeness of 65 ° SR beaten with 40 parts of NBKP and 60 parts of LBKP, 0.5% cationic starch (trade name Mermaid C-50, Shikishima Starch), alkyl ketene dimer (AKD) A paper stock for papermaking was prepared by adding 1.0% of a system sizing agent (trade name Size Pine K-903, Arakawa Chemical Industries) and 13% calcium carbonate and 2% titanium dioxide as filler contents. The following coating liquid 1, coating liquid 2, and coating liquid 3 in which the binder ratio of the coating liquid is fixed to 20 parts with respect to 100 parts of pigment are used on both surfaces of a base paper having a basis weight of 30 g / m ² made from this stock. Then, coated papers of three levels each were manufactured with a test blade coater, and the surface was smoothed with a test super calender to obtain a coated paper for printing.

  The composition of the coating liquid is as follows: 80 parts of primary kaolin (UW-90, Engelhard) as a pigment, 20 parts of light calcium carbonate (trade name Brilliant 15, Shiraishi Kogyo), and styrene as a hydrophobic resin component of 20 parts of binder.・ Dusting prevention using butadiene (SBR) copolymer latex (P-2401R, Nippon A & L Co., Ltd.) and hydrophilic resin components with different mixing ratios of phosphate esterified starch (SK-3000, Nippon Corn Starch Co., Ltd.) Calcium stearate was added as an agent, and modified amine resin, water retention agent, fluorescent dye, and the like were added as printability improvers.

(Coating solution) Coating solution 1 Coating solution 2 Coating solution 3
First grade kaolin 80 parts 80 parts 80 parts (UW-90, Engelhard)
Light calcium carbonate 20 parts 20 parts 20 parts (trade name Brilliant 15, Shiroishi Kogyo)
SBR 6 parts 11 parts 15 parts (P-2401R, Nippon A & L)
Phosphate esterified starch 14 parts 9 parts 5 parts (SK-3000, Nippon Corn Starch)
Appropriate amounts of other additives were added to obtain a solid content concentration of 60%.

Table 2 shows the results of using the RI tester as physical properties of the coated paper obtained, printing evaluation using a general-purpose inkjet printer, and evaluation of offset printing wet strength. The mixing ratio between the hydrophobic resin resin component and the hydrophilic resin component of the binder affects the shape of the backside and dots of the inkjet ink. The higher the ratio of the hydrophilic component, the less likely it is to be backfilled and the better the dot shape. It was confirmed that the higher the hydrophobic component, the greater the amount of back leakage and the tendency of the dot shape to deteriorate. In addition, although the level obtained by the coating liquid is different, the back coating is more difficult to remove as the coating amount is increased, and the dot shape tends to be good. If the coating liquid is less than 5.5 g / m ² , any coating liquid has good ink jet printing suitability. It became clear that I could not be obtained.

  Regarding the wet strength in offset printing, the coating liquid 1 having a hydrophobic resin component of the binder of 10 parts or less of the pigment was inferior in any coating amount, and was evaluated to cause dusting in offset printing. Therefore, the binder which is an appropriate coating composition of the present invention is blended in an amount of 10 to 30 parts by mass per 100 parts by mass of the pigment, and 10 parts by mass or more of the hydrophobic resin component per 100 parts by mass of the pigment. Experimental Example 5 and Experimental Example 6 in which a coating liquid having a hydrophilic resin component ratio of 45:55 to 72:28 is applied in an appropriate application amount range are suitable as the coated paper for offset printing of the present invention. Was confirmed.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, the part and% in an Example and a comparative example show a mass part and the mass%, respectively. Moreover, it measured based on the following evaluation methods about the base paper before application | coating and the obtained coated paper for printing.

<Evaluation method>
(1) Degree of sizing human sizing: Measured based on JIS P8122.
(2) Air permeability resistance: JAPAN TAPPI No. Measured based on 5.
(3) Maximum pore size: Bubble point value P ((kPa): first measured using a Porous Materials Palm Porometer CSF-1100A according to JIS K3932 “Bubble Point Test Method for Microfiltration Membrane Elements and Modules” The pore diameter d obtained from the formula (1) using the pressure when the bubbles are generated is defined as the maximum pore diameter (μm).
d = (4cosφBγ) / P (1)
φ: Contact angle, B: Capillary constant, γ: Liquid surface tension (4) Surface contact angle: Based on TAPPI T458om-84, using FIBRODAT1100 (manufactured by FIBRO system ab), the paper surface and surface tension of 45 mN / m The contact angle was measured at 0.1 seconds, 0.5 seconds, and 1 second for contact time with the liquid.
(5) On-demand printing suitability 1) Back side of water-based ink: printing conditions in on-demand inkjet printing system (Cytex Versa Mark), ink used 1036 (black), back side of solid printing part printed at a printing speed of 150 m / min The back side was visually judged. Judgment criteria are: ◎: Excellent (doesn't lose the back), ○: Good (not almost missed ... allowed), △: Slightly defective (missing), X: Poor (many of missing)
2) Inkjet printing density 1: The density of the solid printing part and the character part in the evaluation method (5) was visually determined. Judgment criteria were: ：: dark, ◯: slightly thin (acceptable), △: slightly poor, x: thin 3) Inkjet print quality: The print quality of the character portion and the solid print portion in the evaluation method (5) was visually determined. Judgment criteria are ◎: excellent, ○: good (acceptable), △: poor, x: remarkably bad (6) general-purpose printer printing aptitude 1) water-based ink back: Epson inkjet printer, paper type as printing conditions: Dedicated OHP sheet, ink: black, mode: recommended setting, 38 points (font: Times New Roman half-width bold) "P" printing back side back side leakage situation was visually determined. The judgment criteria were relative evaluation in the order of ○: good, Δ: bad, x: quite bad, xx: markedly bad.
2) Inkjet dot shape: The dot shape in the evaluation method (6) was visually determined by microscopic observation. Judgment criteria are: ◎: Excellent, ○: Good, △: Slightly bad, X: Bad (7) Offset printing Wet strength: After applying moisture to the sample with a dampening roll using an RI printing machine (Ming Seisakusho) The ink was printed with 0.5 ml of offset printing process ink (GEOS-G Yellow S, manufactured by Dainippon Ink), and the degree of picking on the printed surface was visually determined. Judgment criteria are ◎: Excellent, ○: Good (acceptable), △: Somewhat bad, ×: Bad

<Preparation of paper stock>
(Paper 1) A pulp fiber slurry having a shopper freeness of 35 ° SR beaten with 40 parts of NBKP and 60 parts of LBKP, and 0.5% cationic starch (trade name Mermaid C-50, Shikishima Starch) with respect to the pulp fiber Ketene dimer (AKD) -based sizing agent (trade name Size Pine K-903, Arakawa Chemical Industries) 0.25%, filler content 13% calcium carbonate, titanium dioxide 2% equivalent internal addition 1 Was prepared.
(Paper 2) Paper in the same manner as Paper 1 except that the pulp fiber was beaten to a shopper freeness of 65 ° SR and the filler content was reduced to 10% calcium carbonate and 2% titanium dioxide. Prepared 2 fee.
(Paper 3) The stock 3 was the same as the stock 1 except that the beating degree of the pulp fiber was changed to a shopper freeness of 65 ° SR and the addition amount of the alkyl ketene dimer sizing agent was increased to 0.5%. Was prepared.
(Paper 4) The same stock 4 as the stock used in the experimental example was prepared in the same manner as the stock 3 except that the amount of the alkyl ketene dimer sizing agent was increased to 1.0%.
(Paper 5) A stock 5 was prepared in the same manner as the stock 1 except that the beating degree of pulp fibers was changed to a shopper freeness of 55 ° SR.

<Preparation of coating solution> Similar to the coating solution of the experimental example, as a pigment, primary kaolin (UW-90, Engelhard), light calcium carbonate (trade name Brilliant 15, Shiroishi Kogyo), hydrophobic binder resin Styrene-butadiene (SBR) copolymer latex (P-2401R, Nippon A & L Co., Ltd.) as a component, phosphate esterified starch (SK-3000, Nippon Corn Starch Co., Ltd.) as a hydrophilic resin component, and other various additives for coated paper These include calcium stearate as a dusting inhibitor, modified amine resins as printability improvers, water retention agents, fluorescent dyes, and the like.

(Coating fluid 1)
First grade kaolin (UW-90, Engelhard) 80 parts Light calcium carbonate (Brilliant 15, Shiraishi Kogyo) 20 parts SBR (P-2401R, Nippon A & L) 10 parts Phosphate esterified starch (SK-3000, Nippon Corn Starch) 10 parts Other various additives for coated paper were added in an appropriate amount to prepare a coating liquid 1 having a solid concentration of 60%.

(Coating fluid 2)
First grade kaolin (UW-90, Engelhard) 80 parts Light calcium carbonate (Brilliant 15, Shiraishi Kogyo) 20 parts SBR (P-2401R, Nippon A & L) 10 parts Phosphate esterified starch (SK-3000, Nippon Corn Starch) 10 parts Anionic surface sizing agent (Polymaron 1308, Arakawa Chemical Industries) 1 part Appropriate amounts of various other additives for coated paper were added to prepare coating liquid 2 having a solid content concentration of 60%.

<Comparative Example 1>
3. Apply coating liquid 1 on each side using a gate roll coating device provided in the middle of the paper machine drying zone on both sides of the base paper made with paper stock 1 on an on-top long paper machine. A coated paper was produced by applying 5 g / m ² , and then a surface paper was smoothed by a super calendar to produce a coated paper for printing. Table 3 shows the physical properties of the base paper and coated paper before coating.

<Comparative example 2>
Using a base paper obtained by papermaking stock 2, except that each increased to F surface 10 g / m 2, ^W surface 7 g / m ² coating amount of the coating liquid 1, coated printing in the same manner as in Comparative Example 1 Manufactured paper was produced. Table 3 shows the physical properties of the base paper and coated paper before coating.

<Comparative Example 3>
A coated paper for printing was produced in the same manner as in Comparative Example 1 except that the coating amount per one side of the coating liquid 1 was increased to 6.5 g / m ² using the base paper made from the stock 3. . Table 3 shows the physical properties of the base paper and coated paper before coating.

<Example 1>
5. Apply coating solution 1 per side using a gate roll coating device provided in the middle of the paper machine drying zone on both sides of the base paper made with an on-top type long paper machine using stock 4 After the coated paper was produced by applying 5 g / m ^{2, the} surface was smoothed by a super calender to obtain the coated paper for offset printing of the present invention. The physical properties of the base paper and coated paper before coating are shown in Table 3.

<Example 2>
A coated paper was produced in the same manner as in Example 1 except that the basis weight of the base paper was reduced using the stock 4 and the surface was smoothed by a super calendar to obtain the coated paper for offset printing of the present invention. . The physical properties of the base paper and coated paper before coating are shown in Table 3.

<Comparative example 4>
Alkyl ketene dimer sizing agent (trade name Size Pine K-903, Arakawa Chemical Industries) was further applied to the base paper made with the stock 5 using a test size press device, and the size was measured. A base paper of Comparative Example 4 with an increased height was produced. Using the coating liquid 1 on both sides of the obtained base paper, 5 g / m ^{2 is} applied per side with a test blade coater to produce a coated paper, and the surface is smoothed with a test super calender and printed. Coated paper was used. Table 3 shows the physical properties and the like of the base paper and coated paper of Comparative Example 4.

<Comparative Example 5>
Comparison in which the stencil surface sizing agent (trade name: Polymaron 360, Arakawa Chemical Industries) was further applied to the base paper by 0.5% on the base paper using a test paper size press machine, and the sizing degree was increased. The base paper of Example 4 was produced. Using the coating liquid 1 on both sides of the obtained base paper, 5 g / m ^{2 is} applied per side with a test blade coater to produce a coated paper, and the surface is smoothed with a test super calender and printed. Coated paper was used. Table 3 shows the physical properties and the like of the base paper and coated paper of Comparative Example 5.

<Example 3>
Except for the basis weight, in the same manner as in Comparative Example 5, a styrenic surface sizing agent (trade name: Polymaron 360, Arakawa Chemical Industries) was further added to the base paper on which the stock 5 was made, and 0.5% of the base paper with a test size press device. The coated paper is produced by applying 8 g / m ² per side with a test blade coater using the coating liquid 1 on both sides of the base paper that has been coated with a high degree of size. The coated paper for offset printing according to the present invention was smoothed. The physical properties of the base paper and coated paper are shown in Table 3.

<Comparative Example 6>
The coating liquid 2 is applied to both sides of the base paper made with the paper 5 at a rate of 5 g / m ² per side to produce a coated paper, and then the surface is smoothed by a super calender to apply the coating layer. A coated paper for printing in which a sizing agent was added to was prepared. Table 3 shows the physical properties of the base paper and coated paper before coating.

  Comparative Examples 1 to 3 are examples in which both the maximum pore diameter, the surface contact angle, and the surface contact angle of the base paper in which the sizing agent was internally added were out of the appropriate range, and the coating amount of the coating layer was Even if it is at least appropriate, neither good ink-jet printability can be obtained. Comparative Examples 4 and 5 are coated papers applied to a base paper to which a sizing agent is internally and externally added. Comparative Example 4 is suitable for the maximum pore diameter, but the surface contact angle is When a base paper smaller than the appropriate range is used, as in Comparative Examples 1 to 3, water-based ink penetrates the base paper and reaches the back surface, causing back leakage, and Comparative Example 5 shows the maximum pore diameter of the base paper, Even when using a base paper with both surface contact angles in an appropriate range, if the coating amount is less than the appropriate range, no back-stain will occur, but due to poor penetration of water-based ink, printing density is high, but density unevenness occurs. This indicates that the print quality is deteriorated and good ink jet printability cannot be obtained. Comparative Example 6 is an example in which a coating layer showing a high surface contact angle is formed by adding a sizing agent to a coating liquid on a base paper having a small surface contact angle although the maximum pore diameter is within an appropriate range. An example in which poor penetration of water-based ink occurred and the density unevenness of printing was evaluated to be significantly inferior to that of Comparative Example 5 is shown.

Examples 1 and 2 use pulp that has undergone beating treatment, and apply a coating liquid of an appropriate composition to an appropriate coating amount on a base paper having an appropriate maximum pore diameter and surface contact angle by internal addition of a sizing agent. By forming the working layer, excellent ink jet aptitude as well as excellent offset printing aptitude are achieved. Example 3 uses a pulp with advanced beating treatment, and by combining the internal addition and external addition of the sizing agent, the maximum pore diameter and the surface contact angle of the base paper are in an appropriate range, thereby providing excellent offset printing. This shows an example of achieving aptitude and good ink jet aptitude.

Claims (3)

In a coated paper for printing having a basis weight of 40 to 55 g / m ² in which a coating liquid mainly composed of a pigment and a binder is applied to both surfaces of a base paper, a JIS K 3832 “microfiltration membrane” The contact angle at a contact time of 0.1 seconds with a liquid having a maximum pore diameter of 1 to 10 μm and a surface tension of 45 mN / m determined from the bubble point value measured according to “Bubble point test method of element and module” is 55 to 70. A coated paper for offset printing, wherein a coated layer is formed on a base paper having a thickness of 5.5 to 10 g / m ² per side.   The base paper is made by adding an alkyl ketene dimer sizing agent as a filler and sizing agent to a pulp fiber for papermaking with a shopper freeness of 55 ° SR or higher, and the coating layer is coated on-machine with the coating liquid. The coated paper for offset printing according to claim 1, which is provided. The coating layer is 10 to 30 parts by mass of the binder per 100 parts by mass of the pigment, the hydrophobic resin component of the binder is 10 parts by mass or more per 100 parts by mass of the pigment, and the mixing ratio of the hydrophobic resin component and the hydrophilic resin component of the binder is 45. It is: 55-72: 28, The coated paper for offset printing of Claim 1 or 2 characterized by the above-mentioned.